A semiconductor storage device exhibiting improved programming reliability is provided. In the disclosure, flash memory includes a storage controller and a NAND type storage device. The storage controller includes a voltage detecting part, SRAM, RRAM, and a writer/selector. The voltage detecting part detects whether a power supply voltage drops to a fixed voltage. The SRAM stores a conversion table for converting a logical address into a physical address. The RRAM stores the logical address of a block and a page currently being programmed and conversion information for converting the logical address into another physical address when the fixed voltage is detected by the voltage detecting part during a programming process. The writer/selector converts the inputted logical address into the physical address according to the conversion table or the conversion information of the RRAM and programs data on the page of the block selected according to the converted physical address.